1. Field of Endeavor
The present disclosure relates to a camera module, an auto focus method and an auto focus calibration method.
2. Background
This section provides background information related to the present disclosure which is not necessarily prior art.
Generally, a camera module has a miniaturized size and is applied to mobile communication devices and various IT devices including camera phones, PDAs and smart phones.
In a case the camera module mounted with an actuator moves a lens barrel to perform an AF (Auto Focusing), a best focusing position is sought after by moving the lens from infinity to macro.
Referring to FIG. 1, a conventional camera module has an auto focusing object fixed to a center region (A), whereby, in a case an auto focus calibration is required during manufacturing of the camera module, the auto focusing is carried out based on a numerical resolution value at the center region.
At this time, as illustrated in FIGS. 2a and 2b, a resolving power is measured by increasing an actuator current (actuator driver digital analog converter (DAC) code) of a camera module (11) using a resolving power charts (10, 20) for macro and infinity, and a code with a highest resolving power, that is, best focus points are designated as auto focus calibration codes respectively for infinity and macro. Successively, the values thereof are stored in a memory embedded in the camera module.
FIGS. 3 through 6 are graphs of the numerical value of center resolving power versus the voice coil motor (vcm) current. FIGS. 5 and 6 depict the values for the center, left upper 0.6 field, right upper 0.6 field, left under 0.6 field and right 0.6 field on a single graph.
Generally, a mobile terminal mounted with a camera module downloads the infinity and macro auto focus calibration codes stored in the memory, performs an auto-focus-scan from the infinity auto focus calibration code to the macro auto focus calibration code, and finds a position best suitable for focusing.